type.field_update_forbidden: An update changes a field that stays fixed once its record exists, such as a user field a grant names or a field marked immutable: true

An update changes a field that stays fixed once its record exists, such as a user field a grant names or a field marked immutable: true.

Area 9, Policy; not declinable; the next step is usually the agent's.

Why Jadpo refuses it

A user field that a grant names, such as Note.owner_id in read: [owner_id], decides who a record belongs to. Changing it in an ordinary update would hand the record to someone else, under the grants for editing it. Handing a record over is a decision of its own, so it is a named action, listed under actions: with who may run it.

A field marked immutable: true keeps the value its record was created with, so no update may change it either.

What it looks like

main.jadpo:

example

type Handle = Text {    max_length: 40}entity User {    id: Uuid    handle: Handle {        unique: true    }}principal {    user: {        subject: User.handle    }}type NoteText = Text {    max_length: 200}entity Note {    id: Uuid    owner_id: User.id {        on_delete: OnDelete.cascade    }    text: NoteText    policy: {        read: [owner_id]        update: [owner_id]    }}action give_note(note_id: Note.id, to: User.id) fails NoteNotFound, UserNotFound -> Note {    return attempt Note.update(note_id) {        set: {            owner_id: to        }    }}

jadpo checkcheck failed: 1 error, 1 file

error Note.update changes Note.owner_id, which an update can't change

--> main.jadpo:38:13

   |38 |             owner_id: to   |             ^^^^^^^^ named in policy

reason: Note's policy reaches the caller or the tenant through owner_id, so changing it hands the record to someone else. That is a named action, listed with who may call it under actions: in policy.jadpo.
next: Remove owner_id from the update, or list give_note under actions: in policy.jadpo (agent)
rule: type.field_update_forbidden
help: https://jadpo.dev/docs/errors/type.field_update_forbidden

(agent) at the end of the next: line means your coding agent can make the fix itself.

A field marked immutable: true is refused the same way:

example

type Handle = Text {    max_length: 40}entity User {    id: Uuid    handle: Handle {        unique: true    }}principal {    user: {        subject: User.handle    }}type NoteText = Text {    max_length: 200}entity Note {    id: Uuid    owner_id: User.id {        on_delete: OnDelete.cascade    }    text: NoteText    reference: NoteText {        immutable: true    }    policy: {        read: [owner_id]        update: [owner_id]    }}action renumber_note(note_id: Note.id, reference: NoteText) fails NoteNotFound -> Note {    return attempt Note.update(note_id) {        set: {            reference: reference        }    }}

jadpo checkcheck failed: 1 error, 1 file

error Note.update changes Note.reference, which an update can't change

--> main.jadpo:41:13

   |41 |             reference: reference   |             ^^^^^^^^^ immutable

reason: Note.reference says immutable: true: it keeps the value its record was created with.
next: Remove reference from the update, or immutable: true from the field (agent)
rule: type.field_update_forbidden
help: https://jadpo.dev/docs/errors/type.field_update_forbidden

How to fix it

If the update wasn't meant to change the field, remove the field from its set:. Otherwise the fix depends on the field.

If the action hands a note to someone else, list it under actions: with who may hand it over, here the note's current owner. In a project this goes in policy.jadpo:

example

policy {    actions: {        give_note: [Note.owner_id]    }}

The owner of a note may now give it to another user. On give_note's own update, its line replaces Note's update: grant, so nobody else may hand the note over.

If a field marked immutable: true should be able to change, remove immutable: true from it:

example

    reference: NoteText

renumber_note may now change a note's reference, for anyone Note's update: lets in.

Why Jadpo refuses it

What it looks like

How to fix it

Related